| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength cold-rolled steel plate which does not cause an increase in the production cost caused by the adjustment of chemical components, is not effected by the variation of annealing conditions and has little variation in mechanical properties (in particular strength and ductility), and to provide a method for manufacturing the same. <P>SOLUTION: The high-strength cold-rolled steel plate has a component composition including, by mass, 0.05-0.30% of C, 3% or less (not including 0%) of Si, 0.1-5.0% of Mn, 0.1% or less (not including 0%) of P, 0.02% or less (not including 0%) of S, 0.01-1.0% of Al, 0.01% or less (not including 0%) of N, and the balance comprising Fe with inevitable impurities, and has a structure comprising tempered martensite and/or tempered bainite in which ferrite being a soft first phase is contained in an area ratio of 20 to 50%, and the remainder is a hard second phase. The dispersion state of cementite particles existing in the ferrite particle and each having equivalent-circle diameter of ≥0.05 and <0.3 μm is >0.15 and ≤0.50 pieces per 1 μm<SP POS="POST">2</SP>of the ferrite. <P>COPYRIGHT: (C)2013,JPO&INPIT |
